Well, you kinda know what my take on it is. You ARE the one who has to live with the consequences, so I understand that part, it's just that my impression was that you have been urging him to get some kind of help, treatment, for ages. Now he agrees. I am highly skeptical, let's put it that way. Didn't you tell us he didn't exactly cooperate the last time he saw a doctor?
My biggest concern is that he has "won" this round again. And you are going to go through the same misery if he doesn't comply that you went through this time.
He doesn't have to live with you in order to get mental health treatment. And if he is diagnosed with some disorder (and trust me, these days, it's hard to walk into a shrink's office and not walk out with a diagnosis and a prescription), will you then find it impossible to make him leave if his behavior continues as it has? Will you be saying, "But I can't make him leave if he's sick"?
I'm just worried about you. Please don't take this as harsh--you are a kind, loving person, and I just don't want to see you continuing to suffer.